1. Field of the Invention
This invention relates to an apparatus for joining the ends of belt-shaped materials such as rubber-covered cord layers to form pneumatic tires.
2. Background of the Invention
In the tire industry, carcass plies are manufactured as follows. A number of cords laid in parallel are coated with rubber to form a rubber-covered cord layer. The rubber-covered cord layer thus formed is cut at equal intervals at a predetermined angle from its longitudinal direction to provide belt-shaped materials. The belt-shaped materials thus provided are butt-joined through their side edges which are in parallel with the cords.
One example of a conventional apparatus used for practicing the above-described belt-shaped material joining method has been disclosed, for instance, by Japanese Patent Application (OPI) No. 59980/1976 (the term "0PI" as used herein meaning "an unexamined published application"). The apparatus comprises a positioning plate which is caused to go in and out of the gap between the front end of a first belt-shaped material and the rear end of a second belt-shaped material and against which the front end and the rear end are abutted so that the front end and the rear end are made substantially parallel with each other. A pair of lower depressing members extend respectively along the front end of the first belt-shaped material and the rear end of the second belt-shaped material. Retaining plates are provided immediately above and in parallel with the lower depressing members, respectively. Air cylinders move the retaining plates downwardly so that the front end portion of the first belt-shaped material and the rear end portion of the second belt-shaped material are held between the retaining plates and the depressing members, respectively. Another air cylinder moves the lower depressing member for the first belt-shaped material and the retaining plate engaged with the depressing member towards the other lower depressing member, thereby to allow the butt-joining of the front end of the first belt-shaped material and the rear end of the second belt-shaped material. The apparatus can uniformly and positively butt-join belt-shaped materials even if the front and rear ends thereof are not straight.
However, the conventional apparatus is still disadvantageous in the following point. In the apparatus, the confronting surfaces of the retaining plates and the lower depressing members are linear. Therefore, the front end portion of the first belt-shaped material and the rear end portion of the second belt-shaped material which have come out of the confronting surfaces as much as predetermine values are set free during butt-joining. Accordingly, if the front end portion and the rear end portion have been deformed, they are buckled, as a result of which the front end of the first belt-shaped material and the rear end of the second belt-shaped material are partially butt-joined in an unsatisfactory way.